Method and apparatus for performing workpiece inspection with a probe

ABSTRACT

Various techniques are disclosed for controlling the operation of a workpiece inspection procedure using a battery operated probe to contact the workpiece and transmit information back to a controller in a machine tool system. In one embodiment, battery power is applied to the probe transmission circuitry in response to a flash of infrared radiation. In another embodiment, the probe is turned on by touching the probe against a reference surface. In both embodiments, a timer is provided to automatically disconnect the batteries after a predetermined time period. In such manner battery life is prolonged.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 504,137,filed June 14, 1983, entitled, "Method and Apparatus for PerformingWorkpiece Inspection with a Probe", now abandoned, which is acontinuation-in-part application of U.S. Ser. No. 414,734, filed Sept.3, 1982, now U.S. Pat. No. 4,545,106 entitled "Machine System UsingInfrared Telemetering", and U.S. Ser. No. 478,906, filed Mar. 25, 1983,now U.S. Pat. No. 4,578,874 entitled "Apparatus For Detecting ThePosition of A Probe Relative To A Workpiece", both of which arecontinuation-in-part applications of U.S. Ser. No. 259,257, filed Apr.30, 1981 entitled "Apparatus For Detecting The Position Of A ProbeRelative To A Workpiece", now U.S. Pat. No. 4,401,945 all of which areassigned to the assignee of the present invention.

TECHNICAL FIELD

This invention generally relates to workpiece inspection systems and,more particularly, to the use of probes in automated machine tools tocontact the workpiece and provide information relating thereto.

BACKGROUND ART

Automated machine tool systems require a precise means of locatingsurfaces on workpieces. One of the most common methods is to have themachine move a probe into contact with the workpiece and to record theprobe position when contact is made. Probes of this type are known astouch probes. They generally include a stylus for contacting theworkpiece and circuitry which operates to generate an electrical signalwhen the stylus contacts the part. The machine controller can calculateinformation about the shape or location of the part from the X, Y and Zaxes positional data of the probe when the stylus contact generates theelectrical signal.

One of the problems encountered with the use of many of these types ofprobing systems is in the method by which the signal indicating contactby the probe is transmitted back to the controller. It is oftenimpractical to rely on conventional wiring to carry the signal since thewires may interfere with normal machining operations.

The patent literature discloses several probe designs which are adaptedto be used in an automatic machining center where the probes aretemporarily stored in a tool magazine and are connected and removed fromthe spindle by an automatic tool changer mechanism. Representativeexamples of patents disclosing these probes include U.S. Pat. No.4,339,714 to Ellis; U.S. Pat. No. 4,118,871 to Kirkham; and U.S. patentapplication Ser. No. 259,257 entitled "Apparatus For Detecting ThePosition Of A Probe Relative To A Workpiece", filed Apr. 30, 1981 byJuengel, now U.S. Pat. No. 4,401,945 which is assigned to the assigneeof the present invention.

The Kirkham approach is disadvantageous because its radio frequencysignals are susceptible to electromagnetic interference and must be usedwithin a relatively short transmission distance between the probe and areceiver. Among the problems with the probe system of the Ellis patentis that great care must be taken to align the probe and a speciallyconstructed detector on the spindle head in order for the reactivecoupling therebetween to operate properly. The infrared transmissionapproach disclosed in the Juengel patent is far more advantageous.However, it does require that the probe, in most circumstances, containits own power source.

It has also been proposed to use touch probes in turning centers such aslathes, as well as in machining centers. Turning centers differ frommachining or milling centers in that the workpiece is rotated instead ofthe tool. In most turning centers, the tool holders are mounted atspaced locations about a turret which operates to selectively advanceone of the tools towards the workpiece to perform work thereon. Ingeneral, tools for performing outer dimension work on the workpiece aremounted in slots within the turret whereas inner diameter tools such asboring bars are held in an adapter mounted to the turret.

Touch probes used in turning centers have a somewhat different set ofproblems to overcome than probe used in machining centers, although themethod of transmitting the probe signal back to the controller remains acommon concern. One of the problems unique to turning center applicationis that the probes remain fixed to the turret even when not in useunlike the situation with the machining centers where the probes areinserted in the spindle only when they are needed to be used.Consequently, it is not possible to rely on the probe insertionoperation to activate the electronic circuitry therein.

One prior touch probe technique for turning centers utilizes inductivetransmission modules to transmit the probe signal through the turret tothe controller. See, e.g., LP2 Probe System literature of RenishawElectrical Limited. Unfortunately, this technique requires a substantialmodification of the turret in order to utilize the system. Consequently,this approach does not lend itself to be easily used in existingmachines without requiring the expense and machine down time to performthe retrofitting operation.

Also related to this invention, although less directly, is that priorart concerned with wireless transmission of dimensional gauging datasuch as disclosed in U.S. Pat. No. 3,670,243 to Fougere; U.S. Pat. No.4,130,941 to Amsbury and U.S. Pat. No. 4,328,623, to Juengel et al.

DISCLOSURE OF THE INVENTION

The present invention is directed to apparatus and a method ofperforming workpiece probing operations in a manner so as to prolong thelife of the power sources used in these types of probes. According toone embodiment of the present invention the probe is provided with adetector that serves to connect the power source to the probe signaltransmission circuitry when the detector receives a given signal. Meansare provided remotely located from the probe for generating this "turnon" signal and wirelessly transmitting it to the detector in the probe.This signal is generated prior to anticipated use of the probe toinspect the workpiece and may be initiated by the controller in anautomated machine tool. Later, the power source is disconnected. Poweris thus drained from the source only when necessary. This approach isespecially advantageous when the probes are used in turning centerswhere they remain fixed to the turret even though not always used forinspecting operations. However, the broad concepts of this inventionhave applicability in a wide variety of other probing and machine toolsystem applications.

In the preferred embodiment, the machine controller initiates a flash ofinfrared radiation from a head mounted at a convenient location on themachine. As a result, the probe transmission circuitry is enabled andgenerates an IR signal of a given frequency to indicate that the probeis operating properly and ready for use. The controller then proceedswith the inspection operation. When the probe stylus contacts theworkpiece, the frequency of the IR transmission shifts. This shift infrequency is remotely detected and used by the controller to deriveuseful information about of the workpiece. The probe circuitrypreferably includes a timer which shuts off power to the circuitcomponents after a predetermined time period has elapsed from theinitial power up cycle or stylus contact.

Advantageously, the head may serve the dual purpose of transmitting theflash turn on signal and receiving the IR radiation from the probe. Thehead includes an internally contained optical flash device and aphotodetector. An outer face of the head housing preferably includes alens with an IR filter. The IR filter serves to filter out light in thevisible spectrum from the flash during probe turn on procedure. The lensoperates to focus the IR radiation from the probe onto the photodetectorin the head.

In an alternative embodiment, power to the probe circuitry is initiallyapplied when the stylus contacts a reference surface. In operation, themachine moves the probe so that the stylus contacts the referencesurface to initialize the power up cycle. The probe is then used toinspect the workpiece, with the probe operating to transmit signalsrelating thereto back to a remote receiver head.

BRIEF DESCRIPTION OF THE DRAWINGS

These and various other advantages of the present invention will becomeapparent to one skilled in the art upon reading the followingspecification and by reference to the drawings in which:

FIG. 1 is an environmental view showing a probing system made inaccordance with the teachings of this invention in use with an automatedmachine tool;

FIG. 2 is a perspective view illustrating the use of a probing systemutilizing a flash turn on technique according to one embodiment of thisinvention;

FIG. 3 is a perspective view illustrating the use of a probing systemwith a touch turn on technique according to an alternative embodiment;

FIG. 4 illustrates a cross sectional view along the lines 4--4 of FIG. 2of a probe construction according to one embodiment of this invention;

FIG. 5 is a cross-sectional view along the lines 5--5 of FIG. 4;

FIG. 6 is an exploded perspective view of the probe shown in FIG. 4;

FIG. 7 is a perspective view of a flash/receiver head used in oneembodiment of this invention;

FIG. 8 is a cross sectional view along the lines 8--8 of FIG. 7;

FIG. 9 is a top plan view of a circuit board used in the flash/receiverhead of FIG. 7;

FIG. 10 is a schematic diagram of circuitry used in the flash/receiverhead;

FIG. 11 is a schematic diagram of circuitry used in the probe of oneembodiment of this invention that utilizes the flash turn on technique;and

FIG. 12 is a schematic diagram of circuitry used in a probe utilizingthe touch turn on technique.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

I. Overview

FIG. 1 illustrates, in simplified form, a typical machine tool systemutilizing various aspects of the inventive features to be described. Anumerically controlled turning center 10 is shown therein together witha controller 12 for automatically controlling turning operations on aworkpiece 14 according to programmed instructions. Turning center 10typically includes a rotating chuck 16 with jaws 18 thereon for holdingthe workpiece 14. Mounted to a turret 20 are a plurality of tools 22-24for performing work on the inner diameter (ID) of workpiece 14.Typically, ID tools of this sort include an elongated shank portionwhich are held in place in turret 20 by way of adapters 26-28. Inaccordance with the present invention, a workpiece inspection probe 30is mounted to turret 20 in the same manner as tools 22-24. In thisembodiment, probe 30 is mounted to turret 20 by way of adapter 32 whichis identical to adapters 26-28.

As is known in the art, controller 12, among other things, operates torotate turret 20 to bring the desired tool into the appropriate workposition and then moves turret 20 until the tool contacts the workpieceand performs its desired machining operation thereon. Probe 30, on theother hand, is used to inspect the workpiece 14. In this specificexample, probe 30 is known in the industry as a touch probe in that itgenerates an output signal when the probe stylus contacts a surface ofthe workpiece or other object. Suitable resolvers, digitizers or thelike are used to provided signals to controller 12 indicating theposition of the probe 30. Consequently, when the signal from probe 30indicates contact with the workpiece controller 12, can derive usefulinformation about workpiece dimensions, appropriate positioning thereofwithin the chuck, etc.

A. Flash Turn On

Probe 30 contains its own battery power source for supplying energy toits signal transmission circuitry. Batteries, unfortunately, havelimited useful lives. Thus, there is a real need for some means ofpreserving battery life as long as possible. This is especially true forsmaller sized probes used in turning centers. Smaller probes are alsorestricted in the size of the batteries they can use and thusconservation of energy is very important.

One aspect of this invention provides two way optical communicationbetween probe 30 and a flash/receiver head 40. Head 40 is connected tocontroller 12 through an interface 42. When controller 12 determinesthat it is time to use probe 30 for a probing operation it generates asignal over line 44 to interface 42, which in turn generates a controlsignal on line 46 to cause head 40 to transmit a given optical signal toprobe 30. In the preferred embodiment, this optical signal is a highintensity flash of infrared radiation. This flash is sensed by asuitable detector 48 in probe 30 (see FIG. 2). The flash causes detector48 to couple the battery power to the probe transmission circuitry.Preferably, probe 30 responds to the flash by transmitting IR radiationat a given frequency back to head 40 via light emitting diodes (LED's)50-54. This IR radiation is received by head 40 which, in turn, suppliesa signal to controller 12 via interface 42 indicating that the probe 30is operating properly and ready to perform its inspection operation.

Controller 12 then causes turret 20 to advance probe 30 until the stylus56 contacts workpiece 14. Probe 30 responds to stylus contact bycreating a shift in the frequency of the IR radiation transmitted byLED's 50-54. The shift in frequency is detected by interface 42 andcommunicated to controller 12. The workpiece inspection operationcontinues as desired, with probe 30 transmitting frequency shifted IRradiation to head 40 every time the stylus makes contact.

Probe 30 includes timing means therein which will disconnect the batterysupply from the transmission circuitry after a predetermined period oftime. This time period begins when battery power is initially applied tothe circuitry and is reset every time the stylus contacts the workpiece.Thus, after the probing operation is finished the time period willeventually lapse and the battery power is disconnected from thetransmission circuitry. Accordingly, the battery power is only usedduring periods of anticipated probe usage. Whenever the probe is not inuse the battery power is disconnected and thus, conserves energyprolonging periods between battery replacement.

B. Touch Turn On

FIG. 3 illustrates an alternative method of prolonging battery life. Inthis example, battery power is first connected to the probe transmissioncircuitry by touching the probe stylus 56 against any known referencesurface 60. Reference surface 60 can be any fixed point within machine10 whose location is known by controller 12. Probe contact with surface60 couples the batteries to the probe transmission circuitry andinitiates the transmission from LED's 50-54 to head 40'. Head 40' islike head 40 previously described except that it does not need the flashmeans therein, nor does probe 30' require the photodetector 48.Otherwise, the two embodiments operate substantially identically. Afterinitialization, the probe is moved into position for inspectingworkpiece 14, with probe 30' transmitting frequency shifted signals tohead 40' whenever stylus contact is made. After a predetermined periodof time from the last stylus contact, the batteries are disconnectedfrom the probe transmission circuit.

II. Probe Construction

FIGS. 4-6 illustrate in more detail the construction of probe 30. Theprobe housing is characterized by a generally cone-shaped middle portion70 and a rearwardly projecting shank or cylindrical portion 72 ofreduced cross-sectional diameter. In this specific embodiment,cylindrical portion 72 is hollow measuring about 4 and 1/4 inches inlength, with an outer diameter of about 1.4 inches.

The outer dimensions of cylindrical portion 72 are chosen to generallycorrespond with the dimensions of the bodies or shanks of tools 22-24.Consequently, probe 30 may be used in place of one of the tools inturret 20 and held in adapter 32 in the same manner. As shown mostclearly in FIG. 4, this may be accomplished by sliding cylindricalportion 72 into the pocket 74 of adapter 32 until the rear wall 76 ofhousing portion 70 abuts the front face 78 of adapter 32. This procedurethereby insures that the tip of stylus 56 is spaced at a known positionwith turret 20. Consequently, controller 12 may accurately rely upon theposition of the stylus 56 during the probe inspection operation. Ofcourse, other conventional means may be used to position stylus tip 56at the appropriate spacing. For example, some machine tool systemsutilize a set screw (not shown) or other means within the rear of pocket74 to adjust the stylus spacing.

Cylindrical portion 72 advantageously serves the dual purpose ofproviding a battery compartment as well as to provide an easy to usemounting member. The elongated cylindrical shape of portion 72 enablesthe use of long life "cylindrical" batteries resembling typicalflashlight batteries in shape for powering the probe transmissioncircuitry. Preferably, two "C" cell lithium batteries 80, 82 areemployed. The ability to use cylindrical batteries, instead of smallerbatteries such as button or disc cells, provides the probe with anexceedingly long operational life at low cost.

Batteries 80, 82 are slid into the interior of portion 72. A springloaded cap 84 is then threaded onto the end of portion 72, with spring86 urging the positive or male terminal 88 against board 90. The lowersurface of board 90 includes a circular conductive layer 92. Board 90 issecured within a well 94 in an interior surface of wall 76 by way ofscrews 96. An insulated lead 98 makes electrical connection withconductive layer 92 by way of a plated through hole in board 90. Theopposite end of lead 98 is connected to circuit board 100 containing theprobe circuitry. A description of the electrical schematic for thecircuitry will be described later herein. Circuit board 100 is generallycircular in shape containing electrical components mounted on both sidesthereof. Circuit board 100 is mounted within the interior of middleportion 70 by way of suitable fasteners 102 passing through standoffs104. The board 100 also includes a centrally located aperture 106therein through which various leads can pass to facilitate connection tothe appropriate areas of circuit board 100.

Photodetector 48 and its associated subassembly is mounted in the outersloping surface 110 of middle housing portion 70. Photodetector 48, inthis particular example, is a PIN diode such as part No. DP104 availablefrom Telefunken. Photodetector 48 fits within a countersunk bore and isheld in place by way of a bezel 112 having a window therein. Interposedbetween bezel 112 and photodetector 48 are layers of transparent plastic114, an infrared filter layer 116 and an O-ring 118. Suitable fasteners120 sandwich all of these components into a subassembly mounted withinthe countersunk bore. The leads from photodetector 48 pass throughaperture 106 and are connected to suitable points on circuit board 100.

LED's 50-54 are mounted adjacent to photodetector 48. LEDs 50-54 aredesigned to emit optical signals in the infrared radiation band, i.e.light which is not normally visible to the human eye. LED's 50-54 maycomprise, for example, component Nos. OP290 available from TRW, Inc. Itshould be noted at this point that the arrangement of LED's 50-54 andphotodetector 48, taken together with the configuration of the slopingprobe surface to which they are mounted combine to optimize severalimportant advantages. For example, by mounting LED's 50-54 onto thesloping surface 110 of the probe, the infrared radiation that is emittedthereby is directed forwardly of turret 20 at angles at which theradiation may be easily picked up by various locations of head 40. Theprobe construction enables the user to rotate the probe into a positionwhere the LED's 50-54 and photodetector 48 are pointing in the generaldirection of head 40. Thus, it is not necessary to mount head 40 at anyabsolute spatial location relative to probe 30 giving the system greatflexibility for use in different machine tool systems. Reliable opticalcommunication between probe 30 and head 40 is thereby obtained while atthe same time minimizing the number of light emitting devices withinprobe 30. By keeping the number of light emitting devices to a minimumthe energy drain from the batteries is kept as small as possible,thereby further prolonging battery life.

Rounding out the assembly of middle portion 70, the wall 76 is affixedto rearward portions of portion 70 by way of suitable fasteners 122.O-rings, such as ring 124, are advantageously used to seal the interiorof the probe 30 from the somewhat adverse conditions that the probe mayencounter during use in the machine tool system.

An annular nosepiece 130 includes a threaded male member 132 which mateswith threads formed in a bore 134 in the front face of middle housingportion 70. O-ring 136 is again employed for sealing purposes. Nosepiece130 may be made in various lengths to increase or decrease the relativespacing of stylus tip 56 as may be desired. Due to the threadedfastening engagement with the middle housing portion 70, a variety ofsuch nosepieces can be made and interchanged with one another for use indifferent applications.

A switch unit 140 is removably attached to nosepiece 130. Switch unit140 includes a circular whistle notch end construction 142 including asurrounding O-ring 146 which is press fit into the internal passageway146 within nosepiece 130. One or more set screws 148 extendingorthogonally through nosepiece 130 clamps the switch unit 140 in place.Switch unit 140 can be a variety of constructions that operate to openor break one or more electrical contacts therein when stylus 56 is movedfrom its rest position. Those skilled in the art are aware of a varietyof constructions that fulfill this general purpose. One suitable switchconstruction is disclosed in detail in U.S. Ser. No. 388,187, filed June14, 1982, by Robert F. Cusack, now U.S. Pat. No. 4,451,987 and assignedto the assignee of the present invention. Ths patent is herebyincorporated by reference. Briefly, this construction employs a wobbleplate with three equally spaced ball contacts thereon. The wobble plateis spring biased so that the balls are normally pressed against threecorresponding electrically conductive inserts. The three ball-insertpairs serve as switches (referred to later herein as switches S1-S3) andare connected together in series. The wobble plate is connected tostylus 56. Whenever stylus 56 moves, the wobble plate tilts and liftsone of the ball contacts from its corresponding insert thereby breakingthe electrical connection therebetween.

The three switches in unit 140 are connected to circuitry on board 100by way of cable 150. The other end of cable 150 includes a miniaturecoax connector 152 or other suitable connector that mates with aconnector on the end of replaceable switch unit 140. Those skilled inthe art appreciate that these types of switch units are very sensitiveand may need to be replaced. The construction of the present inventionenables such replacement to be made quickly and easily.

Various shapes and sizes of styli may be used in connection with probe30. For example, instead of the straight stylus 56 shown in thedrawings, a stylus may be used in which the tip thereof is offset fromthe major longitudinal axis of probe 30. The various styli areinterchangeable with switch unit 140 and may be attached thereto by theuse of suitable fastening means such as set screws.

III. Flash Turn On

A. Flash/Receiver Head

The mechanical details of flash/receiver head 40 are shown most clearlyin FIGS. 7-9. Head 40 employs a generally rectangular container 160having an opening 162 formed in a front face 164 thereof. One or morecircuit boards 166 are mounted within container 160. Circuit board 166includes a variety of electrical components thereon for carrying out thefunctions to be described later in detail. Two of the most importantcomponents are shown in these drawings. They are xenon flash tube 168and photodetector 170. As noted before, the purpose of flash tube 168 isto generate a high intensity light pulse of short time duration toinitiate probe operation. Xenon is preferred because it generates lightthat is rich in infrared radiation. In the preferred embodiment, flashtube 168 is a part No. BUB 0641 xenon flash tube available from Siemens.It is capable of generating a flash or light pulse lasting about 50microseconds with an intensity of 100 watt/seconds. Other types ofsuitable light sources, of course, can be employed.

Although not absolutely necessary, the visible light generated by flashtube 168 is preferably eliminated so as not to distract the operator orothers in the shop where machine tool 10 is being used. To this end, aninfrared filter 172 covering opening 162 is employed. IR filter 172serves to block out visible light but passes infrared radiationtherethrough generated by flash tube 168.

The purpose of photodetector 170, on the other hand, is to detectinfrared radiation transmitted by probe 30. In this embodiment,photodetector 170 is a PIN diode and operates in a similar manner asphotodetector 48 in probe 30. A convex lens 174 is advantageously usedin opening 162 to concentrate the IR radiation from probe 30 ontophotodetector 170 which is located at the focal point of lens 174.Rounding out the construction of head 40, there is supplied atransparent face plate 176. Face plate 176 covers opening 162 and issuitably attached to front face 164 having a gasket 178 sandwichedtherebetween.

B. Flash/Receiver Head Circuitry

FIG. 10 illustrates the circuitry used in the flash/receiver head 40 ofthe preferred embodiment. As noted before, head 40 is coupled tointerface 42 over one or more conductor lines generally indicated by thereference numeral 46.

A 26 volt alternating current (AC) signal is applied to the primary ofstep up transformer T1. Energy from transformer T1 is stored acrosscapacitors C8 and C9 which are, in turn, coupled across the positive andnegative electrodes of xenon flash tube 168. In this embodiment,capacitors C8 and C9 store about 250-300 volts DC when fully charged.

To cause tube 168 to flash, controller 12 via interface 42 generates anappropriate signal level on the lines labeled "control" to cause LED 171to conduct and emit light. LED 171 is part of an optical isolationpackage containing silicon controlled rectifier (SCR) 173. SCR 173 isconnected in a series circuit with the primary of transformer T2 andcapacitor C10. Capacitor C10, like capacitor C8 and C9 is charged due tothe action of transformer T1. When LED 171 is activated, SCR 173conducts and dumps the charge of capacitor C10 across the primary oftransformer T2. This charge is stepped up to about 4,000 volts bytransformer T2 whose secondary is connected to the trigger electrode 175of flash tube 168. Trigger electrode 175 is capacitively coupled to tube168 and the high voltage thereon is sufficient to ionize the gas withinthe tube. The ionized gas is sufficiently conductive to permit theenergy from capacitors C8 and C9 to discharge across the positive andnegative electrodes to create a very high intensity flash of shortduration. After tube 168 flashes the capacitors begin to recharge untilsuch time as another flash initiating control signal is supplied frominterface 42.

The probe 30 responds to the flash by transmitting the IR signal whichis picked up by the photodetector 170 in head 40. Photodetector 170 iscoupled to a tuned tank circuit comprising variable inductor L1 andcapacitor C2. By the way of a specific example, probe 30 will generateIR radiation pulsed at a frequency of about 150 kilohertz until theprobe stylus contacts an object at which time the frequency will shiftto about 138 kilohertz. The tank circuit in head 40 is tuned toapproximately the average of these two frequencies so that the headcircuitry can detect either one of these probe frequencies but willfilter out extraneous frequencies outside a preselected range or bandwidth.

The remaining circuitry in FIG. 10 is used to amplify the detectedsignal transmitted from probe 30 which is coupled over the "output" lineto interface 42. Briefly, the head amplification circuitry employs afield effect transistor Q1 whose high input impedence matches that ofthe tuned circuit so as to avoid loading problems. Transistor Q2 incooperation with transistor Q1 amplifies the received signal and couplesit to an emitter follower network employing transistor Q3. The amplifiedsignal is coupled to interface 42 over the output line through DC filtercapacitor C6 and resister R7 coupled to the emitter of transistor Q3.

Interface 42 has circuitry therein that operates to detect theseselected probe signal frequencies and will generate outputs tocontroller 12 in response thereto. A first signal is generated toindicate that the probe is operating properly and a second signal isgenerated when the probe stylus contacts an object. Suitable circuitryfor detecting the frequency shift is disclosed in U.S. Ser. No. 414,734,filed Sept. 3, 1982 entitled "Machine System Using InfraredTelemetering" by Juengel now U.S. Pat. No. 4,545,106 and assigned to theassignee of the present invention. This patent is hereby incorporated byreference. Briefly, such circuitry employs a phase locked loop circuitto perform a frequency shift keying operation on the received signalsand activates relays upon detection of either of the selectedfrequencies. However, a variety of other methods of detecting the probesignals is within the skill of the ordinary practitioner.

C. Probe Circuitry

FIG. 11 is an electrical schematic diagram of the circuitry within probe30. PNP transistor Q10 operates as a switch to selectively connect ordisconnect power from batteries 80, 82 to the components used togenerate IR radiation from LED's 50-54. Transistor Q10 is normally in anonconducting state and thus, the batteries 80, 82 effectively see anopen circuit so that energy is not drained from the batteries. However,when head 40 generates its flash of IR radiation, photodetector 48conducts current from the batteries through inductor L10 for theduration of the flash.

The very fast rise time associated with the light pulse from the xenonflash tube provides a unique signal which can be easily discriminatedfrom other light sources in the area of the machine tool. The IR filterat the head 40 excludes most of the visible spectrum so that the flashcannot be seen and become an aggravation to nearby persons. When thefast rise time light pulse reaches the photodetector 48, it is convertedto an electrical pulse across the inductor coil L10. The coil L10 servesas a high pass filter and excludes steady state or low frequency lightpulses such as flourescent lights in the area may produce.

The surge of current through photodetector 48 during the flash creates a"ringing" phenomenon in inductor L10 as is known in the art. Thisringing phenomenon is basically a damped oscillation that lastsapproximately 500 microseconds in response to the flash light pulse ofabout 50 microseconds. The oscillations from inductor L10 are amplifiedand inverted by inverting amplifier 200. The output of amplifier 200 isconnected to the base of transistor Q10. The momentary ringing ininductor L10 caused by the flash creates a forward bias across thebase-emitter junction of transistor Q10 and causes it to conduct. Theconduction of transistor Q10 connects the power from batteries 80, 82 tothe power inputs of the circuit components labled +V in the drawings.When power is applied to oscillator 202 it begins supplying pulses to atime out counter 204. Counter 204 is reset to initialize its time outperiod when the flash is received from head 40. This is accomplished byway of an inverter 206 which inverts the output of amplifer 200 to apositive signal which is shaped by the RC time constant of capacitor C20and resistor R20 into a pulse. This pulse is connected to the resetinput of counter 204 through OR gate means 208. As will appear, time outcounter 204 is also reset whenever the probe stylus 56 contacts anobject reflected by the opening of one of switches S1-S3.

Time out counter 204 is designed so that it will provide a logical lowsignal on its output line 210 as long as it is counting, i.e. not timedout. The logical low signal on line 210 is inverted by inverter 212which, in turn, is connected through diode D20 to the input of amplifier200. As a result, the output of amplifier 200 is latched to a low statethereby keeping transistor Q10 in a conductive state providing power tothe circuit components until such time as counter 204 times out. Thetime out period for counter 204 is chosen to be of sufficient length toallow the controller 12 to begin the actual inspection process with theprobe stylus contacting the workpiece. In general, a time period ofseveral minutes is sufficient for this purpose. The time out period maybe adjusted by way of potentiometer P20 defining the oscillationfrequency for time delay oscillator 202. Higher frequency oscillationsfrom oscillator 202 cause counter 204 to count faster and thus, time outin a shorter time, and vice versa. The generation of various time delaysis, of course, well within the skill of the ordinary practitioner.

Carrier oscillator 220 and divider 222 cooperate to define the frequencyat which LEDs 50-54 transmit their IR radiation back to head 40.Conventionally, oscillator 220 uses a crystal 224 having a knownresonant frequency as a master clock. Oscillator 220 operates to shapethe oscillations from crystal 224 into a form suitable for providingclock pulses to a conventional digital divider such as divider 222.Divider 222 serves as a convenient means for shifting the frequencytransmitted by LEDs 50-54 when the probe stylus contacts an object. Inthis particular example, divider 222 operates to divide 1.8 MHz pulsesfrom carrier oscillator 220 by the number 12 and thus provides at itsoutput signal frequencies of about 150 KHz. The output of divider 222 iscoupled to a driver transistor Q12 or other suitable circuitry fordriving LEDs 50-54 at the frequency defined by the divider output. Thus,in this example, when head 40 initiates the flash turn on sequence,probe 30 responds by starting the transmission of IR radiation at agiven frequency. The probe transmission is detected by photodetector 170in head 40 which, in turn, supplies an indication to controller 12 thatthe probe 30 is operating properly and is ready to initiate the probingsequence. If probe 30 does not respond in such manner suitableprecautionary measures can be taken.

When the probe stylus 56 contacts an object, one of the three switchesS1-S3 in switch unit 140 will open. The opening of one of the switchesS1-S3 causes two things to happen. First, it resets time out counter 204to the beginning of its time out sequence. Secondly, it creates a shiftin the frequency transmitted by LEDs 50-54. This may be accomplished ina variety of manner. However, in the preferred embodiment, the openingof one of the switches S1-S3 causes comparator 228 to go high. Theoutput of comparator 228 is coupled to the reset input of counter 204through OR gate 208 and thus, resets the counter. In addition, theoutput of comparator 228 is coupled to a frequency shift keying input ofdivider 222 over line 229 to cause it to divide the clock pulses fromcarrier oscillator 220 by a different number, here by the number 13. Theoutut signals from divider 222 thereby changed in frequency to about 138KHz. Thus, the frequency of the IR radiation transmitted by LEDs 50-54is shifted in comparison to the frequency transmitted when the probe wasinitially turned on. This shift of frequency is detected byphotodetector 170 and transmitted to controller 12 to indicate styluscontact with an object, normally a workpiece surface. Controller 12, byknowing the position of stylus 56 when this signal is received, canaccurately calculate the dimensions of the workpiece or derive otheruseful information.

Controller 12 may move the probe 30 to contact other workpiece surfaces,each time the probe responding by a shift in IR radiation transmittedfrom the probe. The timeout period of timeout counter 204 is chosen sothat it is longer than the time that would elapse between styluscontacts. When the probing operation is completed, controller 12 may goforward with other machining operations as may be desired. There is noneed to generate any further signals to turn off the probe since energyfrom the batteries will be automatically disconnected once counter 204times out. In such case, its output line 210 would go high ultimatelyresulting in the reverse biasing of the base-emitter junction oftransistor Q10. This places transistor Q10 in a non-conducting state. Inthis manner the only drain on the batteries 80, 82 is the leakagecurrent of the semiconductors and the photocurrent of photodetector 48.Typically, this current can be very small, often less than 300microamps. Consequently, the more power demanding components aredisconnected from the battery supply until actually needed foranticipated probe use. Preferably these components are made from CMOSsemiconductor technology to even further conserve drain on the batterieswhen used.

By way of a nonlimited example, carrier oscillator 220 is formed by acrystal controlled transistor Component No. 2N2222, divider 222 is anLM4526 available from National Semiconductor, time delay oscillator 202is formed from one half of an integrated circuit LM2903 available fromNational Semiconductor, and time out counter 204 is an LM4040 alsoavailable from National Semiconductor.

IV. TOUCH TURN ON

The touch turn on technique previously described in connection with FIG.3 may be used as an alternative to the flash turn on technique describedin section III. Both techniques have the same general objective, i.e. toconserve battery life. To a large extent the probe construction andcircuitry for both techniques are similar. A schematic diagram of theprobe circuitry for the touch turn on technique is shown in FIG. 12.This circuitry is like that of FIG. 11 and thus, common referencenumerals will be used to reference common components.

A comparison of the two figures will reveal that the major difference isthe deletion of photodetector 48 and associated inductor coil L10 infavor of resistor R50 and capacitor C50. This circuit also differs inthat it includes a line 231 connected between the probe switches S1-S3and node N1 coupled to the input of inverting amplifier 200. TransistorQ10 is kept in a nonconducting state until such time as one of theswitches S1-S3 opens as a result of the stylus 56 contacting referencesurface 60 (FIG. 3). This is because the switches S1-S3 keep the inputto amplifier 200 at substantially ground level as long as they areclosed; i.e. when the probe stylus is not contacting anything. However,when stylus 56 contacts the reference surface 60 one of the switchesS1-S3 opens and causes capacitor C50 to begin charging. Preferably, thevalues of resistors R50 and R18 as well as capacitor C50 are chosen toprovide an RC time constant that delays the time at which capacitor C50is charged to a voltage sufficient to turn on transistor Q10 after beinginverted by amplifier 200. This requires that the controller 12 hold theprobe stylus 56 against the reference surface 60 for a definite periodof time, for example, about a second. This procedure will insure thataccidental bumps against the probe stylus or other extraneous factorssuch as electrical noise will not erroneously trigger activation of theprobe.

Once capacitor C50 has been sufficiently charged the transistor Q10 willturn on and supply power from batteries 80, 82 to the probe transmissioncomponents. The counter 204 will be reset and supply its output signalover line 210 to latch the transistor Q10 in its conducting state. Inthis embodiment, the divider will initially generate the lower of thetwo output frequencies due to the tripping of comparator 228 while theprobe stylus 56 is contacting the reference surface. The controller 12,however, can be suitably programmed to consider this initial probesignal as an indicator that the probe has properly turned on and isready to proceed with inspecting the workpiece.

Controller 12, knowing that the probe 30' is operating properly, thenmoves onto the workpiece inspection procedure with the stylus 56contacting various workpiece surfaces. Once the stylus 56 is moved awayfrom the reference surface 60 the switches S1-S3 close causing divider222 to drive the LED's 50-54 at the other frequency. As soon as thestylus contacts a workpiece surface, one of the switches S1-S3 opensagain tripping comparator 228. This results in the resetting of counter204. The tripping of comparator 228 also provides an output over line229 to divider 222 to cause its output and therefore the outputs ofLED's 50-54 to shift in frequency. This procedure continues until suchtime as the workpiece piece inspection procedure is finished, with thebattery supply being automatically disconnected from the probe circuitryonce timer 204 times out.

SUMMARY

From reading the foregoing specification, those skilled in the art willcome to appreciate that it discloses several significant advances in theworkpiece inspection art. Each of the embodiments have been described inconnection with the best mode that is currently contemplated forcarrying out their inventive techniques. No attempt, however, has beenmade to list all of the various alternatives or modifications to thegeneral concepts thereof. Such modifications or impovements shouldbecome apparent to the skilled practitioner after a study of thedrawings, specification and claims. For example, it should be apparentthat the flash turn on or touch turn on techniques can be used withdifferent types of probes other than the one specifically illustrated.Therefore, while this invention has been described in connection with aparticular example thereof, its true scope should be measured in lightof the following claims and equivalents thereto.

I claim:
 1. Apparatus for use in a machine tool system, said apparatuscomprising:first means including a probe for sensing information about aworkpiece, said first means including circuit means for transmittinginformation relating to the workpiece to a remote receiver, a powersource, and detector means operative to connect power from the source tothe circuit to enable operation thereof upon receipt of a given signal;second means remotely located from the first means for wirelesslytransmitting the given signal to the detector means to thereby initiatethe supply of power to the circuit; said second means including a flashtube and tube activation means for energizing said tube to create saidgiven signal in the form of a flash of light having an intensity ofsubstantially 100 watt-seconds and a duration of substantially 50microseconds; and said detector means including photodetector meanshaving an electrical characteristic responsive to light, and saiddetector means further including filter means coupled to thephotodetector means for rendering said detector means responsive to saidflash to cause connection of power from the source to the circuit toenable operation thereof while rendering the detector means essentiallyunresponsive to other light sources which may be located in the area ofthe probe; whereby power drain from the source is minimized byselectively using energy therefrom only during periods of anticipateduse.
 2. The apparatus of claim 1 wherein said circuit means includestimer means for discontinuing the supply of power from the source to thecircuit after a predetermined period of time.
 3. The apparatus of claim2 wherein said predetermined period of time is measured from the time atwhich power from the source is initially supplied to the circuit or anindication that the first means has undergone a sensing operation. 4.Apparatus for use in a machine tool system to detect contact with aworkpiece, said apparatus comprising:probe means including a stylus forcontacting the workpiece, circuit means for wirelessly transmittinginformation associated with stylus contact to a remote receiver, abattery power source, and detector means operative to connect power fromthe battery to the circuit to enable operation thereof upon receipt of agiven optical signal; first means remotely located from the probe fortransmitting the given optical signal to the detector means in the probeprior to anticipated usage thereof whereby power drain from the batteryis minimized; said first means including a flash tube having ionizablegas therein, flash tube activation means for energizing said flash tube,said flash tube activation means including capacitive storage meanscoupled to the flash tube, transformer means for charging saidcapacitive storage means, and trigger means for transferring sufficientvoltage from the capacitive storage means to ionize the gas in the flashtube, and said first means further including infrared optical filtermeans for blocking visible light from the flash tube whereby activationof said flash tube generates said given optical signal in the form of ahigh intensity flash of infrared light of short duration; and saiddetection means including photodetector means having an electricalcharacteristic responsive to light, said detector means furtherincluding electrical filter means coupled to the photodetector means forrendering said detector means responsive to said flash to causeconnection of said battery power to said circuit while rendering saiddetector means substantially unresponsive to other light sources whichmay be located in the area of the probe.
 5. The apparatus of claim 4wherein said probe circuit includes a timer that discontinues the supplyof power from the battery after a predetermined period of time haselapsed from the generation of the given signal or stylus contact withthe workpiece.
 6. In a probe for detecting information about aworkpiece, said probe having at least one optical transmitting devicefor transmitting information to remote receiver, electrical componentsfor driving said optical device, and at least one battery for supplyingenergy to the components, wherein the improvement comprises:inputcircuit means containing a photodetector and an inductor coupled to thebattery, operative to generate an output signal of a given amplitude inresponse to a remotely generated flash of light from a flash tube andincluding means to provide said photodetector to be substantiallyunresponsive to other light sources which may be located in the area ofthe probe, and switch means responsive to the output signal forconnecting energy from the battery to the electrical components tothereby enable optical transmission of the information to the remotereceiver, said switch means comprising a transistor which switches toits conductive state upon receipt of the given output signal generatedby the photodetector and inductor.
 7. The appartatus of claim 4 whereinsaid probe further includes:optical transmission means connected to saidcircuit means, operative to transmit infrared signals indicating styluscontact with the workpiece.
 8. The apparatus of claim 7 wherein saidfirst means further comprises:a housing having said flash tube therein,a photodetector for receiving signals from the probe, and said infraredoptical filter means being located in an opening in a wall of thehousing.
 9. The apparatus of claim 8 wherein said housing furtherincludes a lens for focusing IR radiation from the probe onto thephotodetector.
 10. The apparatus of claim 7 wherein said probe circuitis operative to generate a given frequency for driving the opticaltransmission means when power from the battery is first applied, and forshifting the frequency when the stylus contacts the workpiece.
 11. Amethod of using a battery powered probe in a machine tool system, saidmethod comprising:using a flash tube to generate an optical signal inthe form of a high intensity flash of light prior to anticipated usageof the probe, said flash having an intensity of substantially 100watt-seconds and a duration of substantially 50 microseconds; filteringvisible light from the flash and transmitting it to the probe; employingcircuitry in the probe that will provide a given output signal inresponse to said flash while being substantially unresponsive to otherlight sources which may be located in the area of the probe; and usingsaid output signal to couple power from the battery to electricalcomponents within the probe for a period of time sufficient to enablethe probe to perform desired operations on a workpiece.
 12. The methodof claim 11 which further comprises the steps of:transmitting an opticalsignal of a given frequency from the probe when power from the batteryis initially supplied to the circuit components; and shifting thefrequency of said transmitted optical signal when the probe contacts theworkpiece.
 13. The method of claim 11 which further comprises the stepof:discontinuing the supply of power from the battery to the circuitcomponents after a predetermined period of time has elapsed from thedetection of said optical signal or probe contact with the workpiece.14. A probe for detecting information about a workpiece, said probecomprising:circuit means for wirelessly transmitting information aboutthe workpiece to a remote receiver; a battery power source; a transistorbetween the battery and circuit means; and detector means operative togenerate a pulse to the transistor to bias it into a conducting state toinitiate the supply of power from the battery to the circuit means toenable operation thereof upon receipt of a high intensity flash ofinfrared radiation generated from a flash tube, said detector meansincluding photodetector means having an electrical characteristicresponsive to light; and filter means coupled to the photodetector meansfor rendering said detector means responsive to said flash to causeconnection of battery power to the circuit means while rendering saiddetector means substantially unresponsive to other light sources whichmay be located in the area of the probe, said probe further includingtimer means enabled by the pulse to generate output signals for a giventime period, said output signals being used to latch the transistor intosaid conducting state to thereby maintain power to the circuit until thetimer means times out.
 15. The probe of claim 14 wherein said filtermeans comprises an inductor coupled to said photodetector means.
 16. Theimprovement of claim 6 which further comprises:timer means forgenerating a latching signal to keep the switch means in a given stateto thereby maintain battery connection for a predetermined period oftime; first means for detecting when the probe contacts an object;second means for generating at least two different frequencies fordriving said optical transmitting device; and said first means beingconnected to the timer means and second means, operative to reset thetimer and create a shift in frequency when the probe contacts an object.17. The improvement of claim 6 wherein the remotely generated flash oflight is infrared radiation provided by the energization of said flashtube and filtration of visible light therefrom.
 18. The improvement ofclaim 6 which further comprises latching means including a timer thatprovides output signals to maintain the transistor in its conductivestate for a given period of time after the receipt of the remotelygenerated flash of light; andwherein the improvement further comprisescircuit means for driving said optical transmitting device, and meanscoupled to the timer and circuit means for resetting the timer andcausing a change in characteristics of the signal emitted by saidoptical transmitting device when the probe contacts an object.